Malaria

Topic Overview

What is malaria?

Malaria is a serious disease that causes a high
fever and chills. You can get it from a bite by an infected mosquito. Malaria
is rare in the United States. It is most often found in Africa, Southern Asia,
Central America, and South America.

What causes malaria?

Malaria is caused by a bite from a mosquito
infected with parasites. In very rare cases, people can get malaria
if they come into contact with infected blood. A developing fetus may get the disease from its mother. You cannot
get malaria just by being near a person who has the disease.

What are the symptoms?

Most malaria infections
cause symptoms like the flu, such as a high fever, chills, and muscle pain.
Symptoms tend to come and go in cycles. Some types of malaria may cause more
serious problems, such as damage to the heart, lungs, kidneys, or brain. These types can
be deadly.

How is malaria diagnosed?

Your doctor will order a blood test to check for
the malaria parasite in your blood.

How is it treated?

Medicines usually can treat the illness. But some
malaria parasites may survive because they are in your liver or they are
resistant to the medicine.

Get medical help
right away if you have been in an area where malaria is present, were exposed
to mosquitoes, and get symptoms that are like the flu. These include a high
fever, chills, and muscle pain.

How is malaria prevented?

You may be able to prevent malaria by taking
medicine before, during, and after travel to an area where malaria is present.
But using medicine to prevent malaria doesn't always work. This is partly due
to the parasites being resistant to some medicines in some parts of the
world.

P. vivax, P. ovale, and P. knowlesi may stay in
the liver, requiring further treatment with medicine to prevent
relapses.

How the disease spreads

Malaria is spread when an infected Anopheles mosquito bites
a person. This is the only type of mosquito that can spread malaria. The
mosquito becomes infected by biting an infected person and drawing blood that
contains the parasite. When that mosquito bites another person, that person
becomes infected.

In the United States, people who develop malaria almost always got infected while traveling in parts of the world
where malaria is common. For more information, see the topic
Travel Health.

Symptoms

When symptoms appear

Malaria can begin with flu-like symptoms. In the early stages, infection
from P. falciparum is similar to infection from
P. vivax, P. malariae, and
P. ovale. You may have no symptoms or symptoms that are
less severe if you are partially immune to malaria.

The time from the initial
malaria infection until symptoms appear (incubation
period) typically ranges from:2

9 to 14 days for Plasmodium (P.) falciparum.

12 to 18 days for P. vivax and P. ovale.

18 to 40 days for
P. malariae.

11 to 12 days for
P. knowlesi.

Symptoms can appear in 7 days. And the time
between exposure and signs of illness may sometimes be as long as 8 to 10 months with
P. vivax and P. ovale.

The incubation period may be longer if you are taking medicine to prevent
infection (chemoprophylaxis) or because you have some
immunity due to previous infections.

Variation in symptoms

In regions where malaria is present, people who get infected many times may have the disease but have few or no symptoms.3 Also, how bad malaria symptoms are can vary depending on your general health,
what kind of malaria parasite you have, and whether you still have your
spleen.

Common symptoms of malaria

In the early stages, malaria symptoms are sometimes similar to those of
many other infections caused by bacteria, viruses, or parasites. Symptoms may
include:

Fever.

Chills.

Headache.

Sweats.

Fatigue.

Nausea
and vomiting.

Symptoms may appear in cycles. The time between episodes of
fever and other symptoms varies with the specific parasite you are infected
with. Episodes of symptoms may occur:

Every 48 hours if you are infected with
P. vivax or P. ovale.

Every 72 hours if you are infected with
P. malariae.

P. falciparum does not usually cause a regular, cyclic fever.

The cyclic pattern of malaria symptoms is due to the
life cycle of malaria parasites as they develop, reproduce, and are released from
the red blood cells and liver cells in the human body. This cycle of symptoms
is also one of the major signs that you are infected with malaria.

Other common symptoms of malaria

In rare cases, malaria can lead to impaired function of
the brain or spinal cord, seizures, or loss of consciousness.

Infection with the P. falciparum parasite is
usually more serious and may become
life-threatening.

There are
other conditions with symptoms similar to a malaria
infection. It is important that you see your doctor to find out the cause of
your symptoms.

What Happens

When you're bitten by a
malaria-infected mosquito, the parasites that cause
malaria are released into your blood and infect your liver cells. The parasite
reproduces in the liver cells, which then burst open. This allows thousands of new
parasites to enter the bloodstream and infect red blood cells. The parasites
reproduce again in the blood cells, kill the blood cells, and then move to
other uninfected blood cells.

After the early stages,
life-threatening complications may develop rapidly with P. falciparum and P. knowlesi. If the infected person is not treated, serious complications or death can occur.

But you may recover in a week to a
month (or longer) after being infected with P. vivax,
P. malariae, or P. ovale, even without treatment.

Malaria can be a very serious disease for a
pregnant woman and her developing fetus, for people without a spleen, and for
young children. Medicine choices are limited for a pregnant woman or a
child. Infection with P. falciparum can lead to death
for a pregnant woman and her fetus. For these reasons, a pregnant woman should
not travel to an area where she could get P. falciparum
malaria. Visit the CDC website (www.cdc.gov/malaria/travelers/index.html) to find
out whether malaria is a problem in the country where you will be traveling.

Malaria recurrences

Malaria caused by
P. falciparum may come back (recur) at irregular
intervals for up to 2 years if treatment is not complete.

Malaria
caused by P. vivax and P. ovale
may recur at irregular intervals for up to 3 to 4 years, but medicine can prevent relapses.

P. malariae
can remain in the blood of an infected person for more than 30 years, usually
without causing any symptoms.

Your risk of getting malaria depends on your age, history
of exposure to malaria, and whether you are pregnant. Most adults who have
lived in areas where malaria is present have developed partial immunity to
malaria because of previous infections and so almost never develop severe
disease. But young children who live in these areas and travelers to these
areas are especially at risk for malaria because they have not developed this
immunity.

Pregnant women are more likely than nonpregnant women
to get severe malaria, because the immune system is suppressed during
pregnancy.

Also, pregnant women,
young children, older adults, and people with other health problems are more
likely to have serious complications if they get malaria.

You can
take measures to reduce the risk of malaria if you live in areas where the
disease is present or if you are traveling in these areas.

Malaria is more severe in people who have had their spleen removed
(splenectomy).

When To Call a Doctor

Call a doctor immediately if you have been in an area where
malaria is present, were exposed to mosquitoes, and
develop flu-like symptoms (such as fever, chills, headache, and nausea).

Watchful waiting

Watchful waiting is a wait-and-see approach. If
you get better on your own, you won't need treatment. If you get worse, you and
your doctor will decide what to do next.

Do not wait to call a
doctor if you think you have malaria. Call a doctor immediately.

For people who live for many years in countries where malaria is common
and have some immunity to malaria, watchful waiting is okay for mild malaria
symptoms. Flu-like symptoms may also be caused by many other diseases or health
conditions. Watchful waiting is not appropriate for most travelers. If you have
a question about your symptoms, call your doctor.

Who to see

Health professionals who can check out
symptoms that may be caused by malaria include:

In the United States,
call the Centers for Disease Control and Prevention (CDC) toll-free at
1-800-232-4636 (1-800-CDC-INFO) or visit the CDC's malaria website
(www.cdc.gov/malaria) to receive the most current
information about malaria and appropriate travel precautions. Your doctor or
local health department may also have this information.

Exams and Tests

Doctors use
thick and thin blood smears to find out whether
malaria-causing parasites are in your blood.
These tests should be done if you have been in a region where malaria is present,
you were exposed to mosquitoes, and you have flu-like symptoms.

A blood smear is prepared from a blood
sample.

If the first blood smear does not show the presence of
malaria parasites but your doctor suspects malaria, you should have a repeat
test every 8 to 12 hours for 36 hours.

During treatment, doctors
use blood smears to see whether the number of malaria parasites in the blood is
decreasing.

A blood test that can diagnose malaria rapidly also is available. If this rapid test indicates a person has malaria, the results are usually confirmed with a blood smear.

Other tests

Other useful tests that may be done
include:

Liver function tests, to check for liver
damage.

Complete blood count (CBC), to check
for
anemia or evidence of other possible infections.
Anemia sometimes develops in people with malaria, because the parasites damage
red blood cells.

A
blood glucose test, to measure the amount of a type of
sugar, called glucose, in your blood.

Other tests being developed to diagnose malaria
include genetic tests or other blood tests that highlight parasites by using
special stains. These experimental tests are not as easy to do and are not as
frequently used as blood smears.

In the United
States, malaria is an infectious disease that must be reported to the local or
state health department.

Treatment Overview

Medicine can prevent
malaria and is needed to treat the disease. Several
things influence the choice of medicine, including:

Malaria is rare in the United States. But it
is widespread in other parts of the world. Find out about the risk for malaria
before you travel internationally. The most accurate information about malaria
risk and medicine resistance in specific countries is from the Centers for
Disease Control and Prevention (CDC) and the World Health Organization (WHO).

If you have been in an area where malaria occurs, were
exposed to mosquitoes, and have flu-like symptoms, but tests do not show the
malaria parasite in your blood, the tests should be repeated 3 or 4 times to
confirm that you do not have a malaria infection. During treatment,
tests are repeated to follow the course of the infection and to check whether
the number of parasites is decreasing.

Your age and health
condition are important factors in selecting a medicine to prevent or treat
malaria.
Pregnant women,
children, people who are very old, people who have
other health problems, and those who did not take medicine to prevent
malaria infection require special consideration.

Prevention

Prevention of
malaria involves protecting yourself against mosquito
bites and taking antimalarial medicines. But public health officials strongly
recommend that young children and pregnant women avoid traveling to areas where
malaria is common.

The most current information about
malaria is available from the Centers for Disease Control and Prevention (CDC)
and the World Health Organization (WHO). If you are planning international
travel, you can learn about the risk of malaria in that geographic area and the
medicines recommended to prevent infection by contacting:

The CDC at its toll-free phone number (1-800-232-4636) or
website (www.cdc.gov/malaria/travelers/index.html).

Your doctor or local
health department.

Prevent mosquito bites

To prevent mosquito bites,
follow these guidelines:

Stay inside when it is dark outside, preferably in a screened or air-conditioned room.

Wear protective
clothing (long pants and long-sleeved shirts).

Use insect repellent with DEET (N,N diethylmetatoluamide).
The repellent is available in varying strengths up to 100%. In young children,
use a preparation containing less than 24% strength, because too much of the
chemical can be absorbed through the skin.

Use bed nets (mosquito netting) sprayed with or soaked in an
insecticide such as permethrin or deltamethrin. But make sure that these insecticides still work against the mosquitoes where you are. In some areas, mosquitoes have become resistant to permethrin and deltamethrin. So the bed nets do not offer much protection.4

Use flying-insect
spray indoors around sleeping areas.

Avoid areas where malaria and
mosquitoes are present if you are at higher risk (for example, if you are
pregnant, very young, or very old).

Other steps that may be helpful in reducing the risk of
malaria include using air conditioning and electric fans, wearing protective
clothing, using aerosol insecticides in your house, and taking certain
antimalarial medicines.5

Medicines to prevent malaria

The selection of
medicines to prevent malaria depends on the
geographic region where you may be exposed to malaria
and your health condition (such as being pregnant, being elderly or young,
being sick, or having immunity or resistance to malaria, or having allergies or
sensitivity to the medicine).

If you are going to a location
where malaria is present, it is very important to take preventive medicines and
to follow the correct schedule for taking them. The majority of people who
become infected with malaria do not take preventive malaria medicines or do not
follow the correct dosing schedule.

Medicine to prevent malaria is most effective
if you take the recommended dosage exactly as prescribed and for the length of
time required.

If you are to take the medicine once a week, take it
on the same day of the week each week.

Upon returning from an area
where malaria is present, continue the medicine for the recommended length of
time to ensure that all parasites have been eliminated from your body. You will
need to take the medicine for 1 to 4 weeks after returning.

Malaria vaccines

Scientists are studying
malaria vaccines to see whether the vaccines are
effectively preventing malaria infection. But no vaccine has been approved to prevent malaria.1, 5 Work continues on improving vaccines for preventing
malaria.

Home Treatment

If you plan to travel in remote areas
where
malaria is present, it is very important to take
preventive medicines and to follow the correct schedule for taking them. The
majority of people who become infected with malaria did not take preventive
malaria medicines or did not follow the correct dosing schedule.

If you are going to areas where there is no medical care available, you
can get medicine before you leave and carry it with you while you travel. Your
doctor will give you instructions on how to use the medicine if you should
develop malaria symptoms. This is a temporary measure until you can get medical
care. Seek medical care as soon as possible (ideally within 24 hours).

The most current
information about the prevention and treatment of malaria is from the Centers
for Disease Control and Prevention (CDC) and the World Health Organization
(WHO). Contact the CDC at its toll-free phone number (1-800-232-4636) or website (www.cdc.gov/malaria). The WHO website is www.who.int/malaria.

Medications

You can take medicines called
antimalarials to prevent and treat
malaria. Malaria is a very serious disease, and its
presence in many regions of the world is well known. So if you are traveling to an area where malaria is present, it is important to reduce the risk of infection by taking medicine before you travel, while you are in the area, and after you return home. Which medicine you take is based on:

Your health condition (for
example, whether you are pregnant, elderly or young, sick, or have immunity or
resistance to malaria).

It is important to know which species of parasite is
present, because serious complications may develop rapidly in a person who is
infected with Plasmodium (P.) falciparum. Drug treatment
is based on:

The species of parasite. If you are infected
with P. falciparum,
life-threatening complications can develop rapidly.
Infection caused by one of the other four species of malaria parasite is rarely
life-threatening.

The density of parasites. If the percentage of
red blood cells infected (parasite density) is over 5%, treatment may include
medicines given directly into a vein (intravenously, or IV) rather than
medicine taken by mouth.

Your health condition. You are at higher
risk for having complications if you are pregnant, elderly, very young, or
have a weak immune system. Different medicines may be prescribed for people in
these groups.

Drug resistance in the geographic area where the
infection occurred. For instance, in many areas P. falciparum is resistant to the drug chloroquine.

During malaria treatment, your doctor may
do daily blood smears to follow the course of the infection. Most
medicines for malaria are ones you take by mouth. But you might get intravenous
(IV) medicines if there are complications or your condition gets worse. If there
are no complications, your fever will clear in 36 to 48 hours. And most
parasites will disappear from your blood within 2 or 3 days.

The medicines used may change as malaria parasites develop resistance and as new medicines are developed.

Medicine choices

There are several medicines for preventing and treating
malaria.

Medicines to prevent malaria

A doctor or local health department can consult the CDC for
specific treatment guidelines for your travel destination. Standard medicines
for preventing malaria include:

Doxycycline. You can take doxycycline
if you cannot take mefloquine. Women who are
pregnant and children younger than age 9 should not take this
medicine.

Malarone. Malarone is a combination of two
antimalarial medicines (atovaquone and proguanil). Malarone is taken to prevent
malaria caused by P. falciparum.

Mefloquine. You can take mefloquine to prevent malaria infections unless the malaria parasite in the area you're visiting is resistant to mefloquine. Do not take mefloquine if you
have a history of active or recent
depression or other mental illness, seizures, or some types of heart-rhythm problems.

Medicines to treat infections

Chloroquine is the most effective medicine for
treating a malaria infection caused by P. ovale or
P. malariae parasites. To prevent relapses of infections
caused by these two parasites, continue taking chloroquine after you leave the
area where these parasites are present. Chloroquine is also used
to treat P. falciparum and P. vivax infections in areas where resistance to chloroquine has
not been confirmed.

Coartem is a combination of the two
medicines artemether and lumefantrine. It is used to treat malaria caused by
P. falciparum.

Medicines to treat chloroquine-resistant infections

When a malaria infection is caused by
resistant strains of P. falciparum or P. vivax, treatment may be more
difficult. When treatment with chloroquine does not work, you must take other
medicines. These medicines may include:

Coartem, which is a combination of the two medicines artemether and
lumefantrine. It is used to treat malaria caused by chloroquine-resistant P. falciparum.

Doxycycline, for infections caused by P. falciparum and P. vivax in Thailand
and Kenya.

Malarone, which is a combination of two
antimalarial medicines (atovaquone and proguanil). Malarone is taken to treat
malaria caused by chloroquine-resistant P. falciparum.

Quinine plus an antibiotic such as
clindamycin, doxycycline, or tetracycline for most P. falciparum infections. It should not be used in Southeast Asia, where
quinine effectiveness is declining. It is only somewhat effective in
Thailand.

You can get antimalarials intravenously (IV) if you are unable to take pills. IV delivery is also used for severe malaria. In the United States,
quinidine is the medicine typically used in these
situations.

Antimalarials to prevent recurrences

Some people
have recurring flu-like symptoms for years after the initial malaria
infection. Relapses from infection of P. vivax or
P. ovale are the most common and can be prevented by
taking primaquine.

What to think about

Children who weigh less than
33 lb (15 kg) should not visit an area that has a risk of chloroquine-resistant
malaria.

If you are going to a location where malaria is present, it
is very important to take preventive medicines and to follow the correct
schedule for taking them. The majority of people who become infected with
malaria did not take preventive malaria medicines or did not follow the correct
dosing schedule.

Pregnant women should discuss medicine options
with their doctors.

Other Treatment

Exchange blood transfusions

Exchange blood
transfusions may be considered for treating severe cases of
malaria if:6

The percentage of blood cells infected with
the parasite (parasite density) is greater than 10%.

You have altered mental capacity (severe confusion) due to the
malaria infection.

You have lung or kidney complications.

Exchange blood transfusion is the quickest way to remove
parasites. This procedure involves withdrawing blood from you at the same time
that donor blood is being injected. During this exchange, the amount of blood
in your body stays constant. Quinine is given by needle into a vein
(intravenously) at the same time as the blood transfusion. Parasite density is
checked every 12 hours until it is less than 1%.6

Centers for Disease Control and Prevention (2011).
Treatment of malaria (guidelines for clinicians).
Available online:
http://www.cdc.gov/malaria/resources/pdf/clinicalguidance.pdf.

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